1. Field of the Invention
The present invention relates to a solid-state image sensor and a method of manufacturing the same.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2009-111118 relates to a solid-state image sensor, and describes a manufacturing method of reliably isolating signal charges between photoelectric conversion regions. The manufacturing method forms a first pixel isolation region by doping an impurity into a semiconductor substrate, forms a first epitaxial growth layer on the surface of the semiconductor substrate, and forms a second pixel isolation region to extend through the first epitaxial growth layer and contact the first pixel isolation region.
Japanese Patent Laid-Open No. 2006-93587 relates to a solid-state image sensor, and describes a method of manufacturing the solid-state image sensor, which prevents color mixing due to an increase in number of pixels per unit and suppresses generation of a dark current in an accumulation layer. The manufacturing method forms a photodiode in an n-type semiconductor layer arranged on an n-type semiconductor via a silicon oxide film, forms a p-type pixel isolation region to surround the photodiode, and forms a front-surface side p+ accumulation layer. After that, the manufacturing method forms a back-surface side p+ accumulation layer by implanting ions into the n-type semiconductor layer from its back surface side.
If an isolation region for isolating charge accumulation regions formed on a semiconductor layer from each other is formed by only ion implantation through one (to be referred to as an ion implantation surface hereinafter) of the two surfaces of the semiconductor layer, the width of the isolation region can be wider away from the ion implantation surface. This is because high implantation energy is required to implant ions into a region away from the ion implantation surface (that is, a deep region), thereby widening a region into which ions are implanted. This phenomenon in which the width of the isolation region becomes wider away from the ion implantation surface prevents the density of charge accumulation regions or pixels from increasing.